The objectives of the study of the association of glyceraldehyde phosphate dehydrogenase and phosphoglycerate kinase with erythrocyte membranes include: 1. to determine if these enzymes can be reversibly dissociated from and reassociated with the membrane and to determine the conditions which affect their membrane interactions, 2. to determine the specificity of interaction of the enzymes with the membrane, 3. to determine how interaction of the enzymes with the membrane affects their catalytic activities. The objectives of the study of the structure and function of the purified phosphoglycerate kinase include: 1. to separate the two lobes of the protein by selective proteolytic digestion and to determine the functions of the two lobes, 2. to measure the binding constants for the substrates and activators of the enzyme, and to relate ligand binding to catalytic and regulatory functions of the enzyme.